1. Field of Invention
The invention relates to a motor and, in particular, to a stepping motor with the design of tolerating assembly gaps.
2. Related Art
The rigidity of motor structure has an important influence on the vibrations, noises, and lifetime of the motor. This is because the motor components always have some tolerances in batch productions. If the tolerances are not carefully taken care of, the internal components of the motor may become loose and affect the precision, output stability, as well as lifetime of the motor.
To solve this problem, as shown in FIG. 1A, a conventional motor 1 includes a lower housing 11, an upper housing 12, a rotor 13 and a stator 14. The lower housing 11 has a concave portion 111, and the upper housing 12 has a flange 121 disposed corresponding to the concave portion 111. The upper housing 12 and the lower housing 11 together form an accommodating space 15 for accommodating the rotor 13 and the stator 14. The rotor 13 is disposed corresponding to the stator 14 and has a shaft 131 protruding from the upper housing 12. FIG. 1B is a partially enlarged view of FIG. 1A. As shown in FIG. 1B, when the lower housing 11 and the upper housing 12 are assembled, the flange 121 of the upper housing 12 touches against the concave portion 111 of the lower housing 11 and the upper end surface of the stator 14. The motor tolerates the gap between the flange 121 and the stator 14 due to their tolerances using a gap-tolerating material M between the flange 121 and the upper end surface of the stator 14. Finally, a sealing material S seals the connection between the flange 121 and the concave portion 111. This completes the assembly of the motor 1, and prevents dusts or impurities from entering the motor 1.
However, when a gap-tolerating material M is used to tolerate assembly gaps, it is necessary to consider the motor housing structure. Different motor housing structures require the use of different materials, such as rubber, silicone, plastic or iron sheets. Other factors such as shape and thickness should be considered as well. All these inevitably increase the assembly difficulty and costs.
Therefore, it is an important subject to provide a motor that can tolerate component gaps and ensure good sealing, thereby increasing the reliability and lifetime of the motor, as well as reducing assembly steps and material costs.